Two-Step Magnetic Ordering in Quasi-One-Dimensional Helimagnets: Possible Experimental Validation of Villain’s Conjecture about a Chiral Spin Liquid Phase

Abstract

Low-temperature specific heat, magnetic susceptibility, and zero-field muon spin resonance ($\ensuremath{\mu}\mathrm{SR}$) measurements have been performed in the quasi-one-dimensional molecular helimagnetic compound $\mathrm{Gd}(hfac{)}_{3}\mathrm{NITEt}$. The specific heat presents two anomalies at ${T}_{0}=2.19\ifmmode\pm\else\textpm\fi{}0.02\text{ }\text{ }\mathrm{K}$ and ${T}_{N}=1.88\ifmmode\pm\else\textpm\fi{}0.02\text{ }\text{ }\mathrm{K}$, which both disappear upon the application of a weak magnetic field. Conversely, magnetic susceptibility and $\ensuremath{\mu}\mathrm{SR}$ data show the divergence of two-spin correlation functions only at ${T}_{N}=1.88\ifmmode\pm\else\textpm\fi{}0.02\text{ }\text{ }\mathrm{K}$. These results suggest an experimental validation of Villain's conjecture of a two-step magnetic ordering in quasi-one-dimensional $XY$ helimagnets; i.e., the paramagnetic phase and the helical spin solid phase are separated by a chiral spin liquid phase, where translational invariance is broken without violation of rotational invariance.